12 bit compressed NEF vs. JPEG

Jpeg stores only 8 bits. Unless you get colour and exposure spot on in camera jpeg is not recommended for important shots. RAW allows you to alter the exposure, contrast curve and colour (white balance) after the shot is taken without losing detail. Doing major adjustments to jpeg files will introduce posterization (banding) and/or noise.

For wedding's I'd probably shoot 14 bit lossy compressed RAW, this gives me the full highlight - shadow range to play with but with reasonable sized files. Getting detail in both her white dress and his black suit is a real challenge unless the lighting is exceptionally flat and even. As others have said "lossy" produces no visible difference so there is no reason to bother with the larger file types.

For other occasions if the lighting wasn't too contrasty you could consider 12 bit lossy... but personally I'd rather have too much data / quality than too little.